Why The Best Time To Drink Coffee Is Not First Thing In The Morning

Ryoko from ILoveCoffee.jp explains the science of cortisol and coffee consumption.

Drinking a cup of coffee first thing in the morning blunts the energy-boosting effects of caffeine and may lead to increased tolerance of the stimulant. This counterintuitive fact is explained in engaging visual form by Ryoko Iwata, "a Japanese coffee-lover living in Seattle" on her appropriately titled blog, I Love Coffee. Iwata based her post on research gathered by Steven Miller, a Ph.D. candidate at the Uniformed Services University of the Health Sciences in Bethesda.

Everybody is different, of course, but we are all guided by the 24-hour hormonal cycle referred to as the circadian clock. These basic rhythms are preprogrammed into us genetically and although we can mess with our cycles through lifestyle habits, the major factor in their regulation is sunlight. One of the things that this clock controls in humans is the release of the a hormone called cortisol which makes us feel alert and awake.

Here's the thing. The peak production of cortisol occurs between 8–9 am (under normal circumstances.) This means that at the time that many people are having their first cup of coffee on the way to work, their bodies are actually "naturally caffeinating" the most effectively! According to Iwata, the effects of caffeine consumption at times of peak cortisol levels actually diminishes the effectiveness of the additional stimulation. Worse still, "By consuming caffeine when it is not needed, your body will build a faster tolerance to it, and the buzz you get will greatly diminish."

Cortisol is also considered a stress-related hormone and consumption of caffeine has been shown to increase the production of cortisol when timed at periods of peak cortisol levels. An increased tolerance for caffeine can therefore lead to heightened cortisol levels which can disturb circadian rhythms and have other deleterious effects on your health.

Iwata, as her blog title suggests, loves coffee and has articulated what she considers to be the optimal timing of your coffee intake to experience maximum enjoyment with minimal negative effects. The times of peak cortisol levels in most people are between 8-9 am, 12-1 pm and 5:30-6:30 pm. Therefore, timing your "coffee breaks" (an apt term) between 9:30-11:30 and 1:30 and 5:00 takes advantage of the dips in your cortisol levels when you need a boost the most (see graphic by Iwata below.)

The best times to drink coffee are when your cortisol levels naturally dip. These are, in fact, traditional "coffee break" times.

Put this way, the traditional idea of a "coffee break" makes a lot of sense. I almost wonder if the the idea of having coffee first thing is a habit instilled by the coffee industry to get us to all drink more coffee! What Iwata's chart does not take into account is coffee consumption by early risers before 8 am, when many of us have our first cups. This raises the question of whether to have three coffees a day (probably too much for most people) or to forgo one of the periods Miller's research suggests. I will follow up with him and report back on his response.

UPDATE: Steven Miller, who wrote the original blog post on which this story is based makes it clear that he does not, himself research caffeine, but has taken an interest in the academic research published in this area. His own research "focuses on identifying treatments against seizures induced by the chemical weapons known as nerve agents." He also follows "the electrophysiology of the brain, seizure disorders, and psychiatric disorders." His original post was also published on the Cociety for Neuroscience's BrainFacts blog and referenced on Military Times.

In response to my question about how his formulation applies to early risers, Miller replied, "Military Times asked me about this since most of our military personnel are often up well before that time. Cortisol for these individuals is likely very low compared to when sunlight dramatically increases in the morning. However, there is a phenomenon called the Cortisol Awakening Response (CAR) that results in an approximate 50% increase in cortisol upon awakening. For a review on this topic see: http://www.ncbi.nlm.nih.gov/pubmed/18854200. This would suggest that even these individuals would not need caffeine immediately upon awakening either. However, I would suspect that even for these individuals, they are still waking up hours before their peak cortisol levels and a dose of caffeine would probably help them be more vigilant/alert. Although probably not necessary immediately upon awakening due to CAR, I would still probably say that I'd drink some kind of caffeine about an hour or so after I wake up if I were someone who wakes up 4-5 AM daily."

And in response to my question about the universality of daily cortisol schedule across populations, he writes, "The study I cited where they measured cortisol levels from a group of men was probably men on the same sleep schedules for measurements, exposed to the same light, and a lot of other variables that obviously cannot directly extend to a general population. However, people living in countries where they have a full-day of sunlight and night without light, it is probably a good rough estimate. Again, I think the key to my post is that 1) You don't need caffeine immediately upon waking and 2) For most people, late morning and early afternoons are good times for a caffeine-pick me up. Later times will be effective as well but it will disrupt your sleep (http://www.ncbi.nlm.nih.gov/pubmed/24235903)."